The present invention relates generally to a ferro-sintered alloy exceling in wear resistance at elevated temperatures, and more particularly to a ferro-sintered alloy suitable for use in valve seats of internal combustion engines.
The valve seats for internal combustion engines have heretofore been formed of specialty cast iron or heatresistant steel. In the meantime, a series of drastic exhaust gas regulations have been laid down and enforced for the protection of environment and many improvements have been introduced in the fuel cost and performance of internal combustion engines, correspondingly. As a matter of fact, rigorous requirements have increasingly been imposed upon the use of valve seats. The situation being like this, various materials developed to meet an early stage of regulations can no longer be employed, to say nothing of the aforesaid materials.
During the operation of an internal combustion engine, the valve seats are exposed to high-temperature combustion gases and receive a continuity of impacts from the valves that rotate slowly but reciprocate at high speeds. Accordingly, the valve seat materials have to display excellent wear resistance under such conditions.
In view of the sliding wearing of certain types that the valve seat suffers, the hardness of the materials applied is considered of great importance in the improvement of wear resistance. However, the use of the materials having a greater hardness with a view to preferentially improving the wear resistance gives rise to difficulties in the production, since parts such as valve seats inevitably require mechanical working.
Japanese patent application No. 144325/53 discloses a sintered steel material comprising 25 to 75 weight % of an alloying base A consisting of the following components and 75 to 25 weight % of an alloying base B consisting of the following components, said bases A and B being dispersed in spots.
______________________________________ Base A Base B ______________________________________ Cr 2.about.4% (by weight) Co 5.5.about.7.5% (by weight) Mo 0.2.about.0.4% (by weight) Ni 0.5.about.3% (by weight) V 0.2.about.0.4% (by weight) Mo 0.5.about.3% (by weight) C 0.6.about.1.2% (by weight) C 0.6.about.1.2% (by weight) Fe the remainder Fe the remainder ______________________________________
Although this material has excellent wear resistance over the prior art materials, it is found that unusual wearing sometimes takes place under the present severe conditions; hence, there is left much to desired, in particular as to wear resistance.